Radiotube and method of operating same



July 24, 1928. 1,677,896

E. KOCH I RADIO TUBE AND METHOD OF- OPERATING SAIE Filed' A ril 25, 1925 62/ INVENTOR.

ATTOR EY 0 or stem 7. Secured Patented July 24, 1928.

UNITED STATES PATENT OFFICE.

EARL L. KOCH,

'MQCULLOUGH, OF WILKINSBURG, PENNSYLVANIA.

BADIOTUBE AND METHOD OF OPERATING SAME.

Application filed April 25, 1925. Serial No. 25,903.

This invention relatesto thermionic tubes,

and is for a tube of the equi-potential cathode type wherein the cathode may be energized by an alternating current.

The present invention has thermionic tube in which the to provide a for its object cathode may be heated from a source of alternating current hum. or distortion of the alternating A further object of tube capable of use with alternatprovide a without any undesirable resulting from the action current tield'in the tube. the invention isto ing or pulsating currents which may have superior amplification factors and lower impedance than present types of tubes.

Constructions have heretofore been proosed wherein a cathode on a is heated by means porcelain rod of a resistance element disposed above the plane of the grid and the plate of the tube, whereby its field was suffieiently removed from electron flow between the cathode, grid and plate as to have little effect on the action of the tube, thereby substantially eliminating alternating or pulsating current hum.

Such a construction tages due to the length had some disadvanof the cathode and heater unit, and removed the source of heat to a point where much of the heat would be radiated before it ticularly the end heater. perature gradient reached the cathode, parmost remote from such It also resulted in a noticeable temalong the cathode directly affecting electron emission. I

According to the present invention, the

heater element ina portion of the cathode and to the emitting be in close proximity may extend therethrough without causing undesirable effects The invention may be readily understood by reference to the accompanying drawing,

wherein:

Fig. 1 is In the drawing,

a more or less diagrammatic section through a tube embodying my inventypical circuit diagram for 5 designates a suitable envelope, having a base portion 6 and a lowto the base portion of the envelope is a base 8, preferably of standard construction.

In the upper p art of the envelope is an a porcelain or other suitable rod 11. Fitted over this red is a sleeve 12 COITlPl'lSlIlg the cathode of the tube. A lead wire 13 nm extend from this sleeve or cathode througi the stem 7 and connect with a contact pin 14 on the base of the tube.

Surrounding that portion of the rod through which the resistance heater 10 passes and out of contact with the cathode, is the input grid 15. A lead wire 16 may connect the input grid withcontact pin 17 on the base. At one end of the rod, preferably the lower end, just below the input grid 15, is a small auxiliary grid or auxiliary control electrode 18. This auxiliary grid may connect with a contact pin 19 on the base through a wire 20.

Surrounding the input grid, but out of contact therewith, is the plate or anode 21, which may be of cylindrical or other suitable formation. A. lead wire 22 may connect the anode 21 with a contact pin 23 on the base.

In use, the tube functions as any other tube and'may be used in any of the usual radio tube circuits,as illustrated in the typical diagram of Fig. 2. The heater lead wires However, in order to eliminate alternating current hum that would otherwise result,

low voltage battery C is put in the circuit between the cathode and the auxiliary grid. This battery has its negative side connected with the auxiliary grid, whereby it puts a negative potential or bias on this grid. This effectively eliminates all alternating current noises.

The theory of the tube, as far as the effect of the auxiliary grid is concerned, is not definitely understood, but tubes embodying this feature have successfully demonstrated the practicability of the invention.

It will be understood that the drawing and description merely disclose one embodiment of the invention, and that various changes in the construction and circuits embodying the invention are contemplated and to be considered as being within the scope and spirit of the appended claims.

\Vhat is claimed is:

1. A thermionic tube having an anode, a cathode, a looped resistance heater. for the cathode, a helical control electrode, and a helical auxiliary control electrode adjacent one end of the cathode and adjacent the end of the first control electrode, said helical electrodes consistin of different numbers of turns of substantially the same diameter.

2. A thermionic tube having an anode, a

cathode, a looped resistance heater for the,

cathode extending along the cathode and adapted to be energized by alternating current, a control electrode interposed between the anode and cathode, and an auxiliary control electrode at one end of the first control electrode and separate therefrom.

3. A thermionic tube having an anode, a cathode, a resistance heater for the cathode,

and a plurality of separate helical control electrodes having substantially the same radii and arranged longitudinally of the cathode and extending over distinct areas of the cathode.

4. A radio tube having an anode, a cathode, a looped resistance heater for the cathode extending therealong, a helical control electrode between the anode and the cathode and extending along the anode out of contact with said cathode and anode, and a helical auxiliary control electrode beyond one end of said first control electrode and separate therefrom.

5. A radio tube having an anode, a sleevelike cathode, a porcelain rod extending through the cathode, a looped resistance element within the porcelain rod and Within the cathode and adapted to be energized from a source of alternating current, a grid extending throughout the greater portion of the length of the cathode, an auxiliary control electrode at one end of the first grid and separate therefrom, said auxiliary control electrode extending along a portion of the cathode beyond that portion along which the first grid extends, said grid and auxiliary control being interposed between the cathode and the anode.

6. A thermoinio tube having a refractory supporting element therein, a resistance heater extending throughout the greater por tion of the-length of the refractory supporting element, a sleeve surrounding the refractory supporting element and comprising the cathode of the tube, an anode spaced away from the cathode, a main grid extending trodes extendingalong the cathode and exalong that portion of the cathode which overlies the heater, and an auxiliary grid extending along that portion of the cathode beyond the part that overlies the heater, both of said grids being in the path .of the normal electron flow from the cathode to the anode.

7. A radio tube having an e uipotential cathode, a heater for said ca't ode energized from a source of alternating current, an anode, and a pair of separate control electending along different portions of the length of the cathode, said electrodes consisting of helixes of wire. I

8. A radio tube having a. cathode, an anode,'a heater for the cathode. partially coextensive with the cathode, a main grid extending along the greater portion of the length of the cathode, an auxiliary grid separate from the main grid-and at one end of the main grid and extending along a relatively small portion of the; cathode, both of said grids being between the anode and the cathode and out of contact with each.

9. A radio tube having a cathode, an anode, a resistance heater for the cathode energized from a source of alternating current, a main grid between the anode and cathode extending along the cathode, and an auxiliary grid extending along the oathode beyond one end of the main grid and separate therefrom, and means for impressin a negative potential on said auxiliary grid to thereby eliminate the inductive field produced by alternating currents in the heater.

10. The methodof eliminating alternating current effects in radio tubes having cathodes heated by a resistance element in an alternating current circuit which consists in providing an auxiliary control in the tube and maintaining a negative potential on said auxiliary control element.

11. A radio tube having an anode, a cath ode substantially coextensive with the anode, a looped heater for the cathode having terminals at one end thereof, a helical main control electrode between the cathode and anode, and a helical auxiliary control electrode at one end of the main control electrode and separate therefrom, said auxiliary control electrode being located adjacent the end portion of the cathode and the end portion of the anode.

In testimony whereof I hereunto aflix my signature.

EARL L. KOCH. 

